[ISN] Tester claims 90% of VPNs open to hackers

InfoSec News isn at c4i.org
Tue Feb 8 03:54:44 EST 2005


By Antony Savvas 
8 February 2005 

Security testing company NTA Monitor has claimed that 90% of virtual
private networks are open to hackers.

Over a three-year period of testing VPNs at large companies, NTA
Monitor said 90% of remote access VPN systems have exploitable
vulnerabilities, even though many companies, including financial
institutions, have in-house security teams.

Flaws include "user name enumeration vulnerabilities" that allow user
names to be guessed through a dictionary attack because they respond
differently to valid and invalid user names.

Roy Hills, NTA Monitor technical director, said, "One of the basic
requirements of a user name/password authentication is that an
incorrect log-in attempt should not leak information as to whether the
user name or password is incorrect. However, many VPN implementations
ignore this rule."

The fact that VPN user names are often based on people's names or
e-mail addresses makes it relatively easy for an attacker to use a
dictionary attack to recover a number of valid user names in a short
period of time, said Hills.

Passwords can also be made harder to crack by deploying a mixture of
characters and numbers. Hills said a six-character password can be
cracked in about 16 minutes using standard "brute force" cracking
software. However, a six-character password combining letters and
numbers could take two days to crack.

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